There are presently known a wide variety of processed foods in a tubular shape, such as macaroni made of flour and the Japanese processed food known as "chikuwa" which is made mainly of fish. In addition, in the Japanese Utility Model Application No. 6-4815 the inventor of the present invention proposed a "konnyaku" in a tubular shape similar to the shape of macaroni and chikuwa. "Konnyaku" is a jelly-like Japanese processed food which conventionally takes the shape of a bar of soap or noodle. Specifically, konnyaku is made from "Konnyaku potatoes" including glucomannan. When the glucomannan absorbs water, its expands and becomes an extremely larger volume colloid having high viscosity. When this colloid is added to lime water and other substances and heated, it coagulates as a translucent and elastic lump.
The above mentioned tubular foods are shaped in various manners. For instance, chikuwa is made by applying fish paste to the periphery of a rolling pin and baking or steaming it. Macaroni is shaped by extruding a kneaded mixture of flour and water out of a ring-like opening.
Tubular konnyaku, on the other hand, has not been commercially produced because of technical difficulties. For instance, the method for producing chikuwa is not appropriate for konnyaku. Specifically, the rolling pin around which the konnyaku material would be applied must be removed after the material has coagulated. When the material is konnyaku, it is tremendously difficult to pull away the rolling pin without destroying the desired tubular shape. Therefore, it is not feasible to produce tubular konnyaku, especially with small diameters, through the same method used to produce tubular chikuwa. Even if the tubular konnyaku to be formed is of a relatively larger diameter, the productivity would be too limited to realize commercial production.
The method for producing macaroni is also inappropriate for processing konnyaku since the wall of konnyaku material defining the hollow tubular shape tends to collapse because of its higher flowability, and spoil the desired hollow tubular shape of the final product before it coagulates.